Get the latest available source-linked reference exchange rate for a currency pair (e.g. USD to CNY). Reference data, not a transaction quote.
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | ISO 4217 target currency code, e.g. CNY | |
| from | Yes | ISO 4217 base currency code, e.g. USD |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It discloses that data is source-linked reference data rather than a transaction quote, which is meaningful context. However, it omits freshness/latency details (how 'latest' is defined), error behavior for unsupported pairs, and whether the response needs further interpretation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single compact sentence front-loads the core action and ends with the key disambiguation ('Reference data, not a transaction quote'). Zero waste.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple 2-param read tool this is nearly adequate, but with no annotations and no output schema, the description should say more about what 'latest' means (timestamp/freshness) and how errors are surfaced. It does not.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the schema already documents 'from' and 'to' as ISO 4217 codes with examples. The description adds only the example pair (USD to CNY), which duplicates the schema examples. Baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (get) and resource (latest exchange rate) with scope (reference, not transaction quote) and an example pair. It does not name or contrast with the sibling get_history, which is the natural alternative for historical vs. latest data.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Implies usage via 'latest available' and 'reference data, not a transaction quote,' but never states when to use this tool versus get_history. No explicit when/when-not guidance or alternative routing.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.